Internal Friction on AISI 304 Stainless Steels with Low Tensile Deformations at Temperatures between−50 and 20C

Abstract

Austenitic stainless steels specimens were deformed by tension in temperatures in the range of−50Cto 20Cand 0.03 to 0.12 true strain, in order to obtain different volumetric fractions ofε(hexagonal close packed) andα′(body centered cubic) strain induced martensites. The morphology, distribution and volumetric fractions of the martensites were characterized by metallography and dilatometry analysis and quantified by ferrite detector measurements. The damping behavior of specimens with different volumetric fractions of martensites was studied in an inverted torsion pendulum in the 40Cto 400Crange. Theε- andα′-martensites reversion was observed in the temperature range of 50C–200Cand 500C–800C, respectively, by dilatometry. Internal friction curves in function of temperature of the deformed samples presented internal friction peaks. The first internal friction peak is related to sum of the amount ofε- andα′-martensites. For low deformations it aligns around 130Cand it is related only to theε→γreverse transformation. The peak situated around 350Cincreases with the specimen degree of deformation and is, probably, related to the presence ofα′/γinterfaces, and deformed austenite.